This invention relates to an antifriction bearing assembly having a speed sensing system that produces an output signal. More specifically, it relates to an antifriction bearing assembly speed sensor for use with a rotatable shaft whose speed can be controlled through a feedback system utilizing the speed signal as a basic input to the feedback system. This invention is especially well-suited for use with an automobile wheel bearing in order to provide a speed signal to, for example, an anti-lock braking system or a traction control system.
It is a goal of the automotive industry to manufacture such bearings in a manner which protects the speed sensor and an associated encoder, as well as any rolling elements, from the environment, e.g., from water, dust, and road debris. One way to effectively do this is to position the encoder between two annular rows of rolling elements and then position the sensor assembly so as to be aligned with the encoder.
An example of prior art which does this is U.S. Pat. No. 3,793,545 for a "Speed Sensing Apparatus" issued to Heinz Leiber et al on Feb. 19, 1974. Leiber et al disclose a connecting housing (7) which is screwed into an axle housing (1) so as to be aligned with a rotor ring (3) pressed onto a drive shaft (2)--see FIG. 3, especially.
Another example of the prior art is U.S. Pat. No. 4,778,286 for a "Bearing Assembly" issued to Satoshi Kadokowa on Oct. 18, 1988. In FIG. 1, Kadokawa discloses a bearing assembly having a pulser gear (50) positioned in an annular gap defined by an annular member (16) and the end surface of the shoulder of the body (14). A sensor (60) is inserted in a through-hole.
One of the main problems with the prior art is that the encoder is positioned in such a manner that it must carry a substantial axial load; therefore, the encoder must be made with a strong material capable of withstanding these forces.